An optical disk consists of a first laminated layer structure and a second laminated layer structure. The first structure has a first transparent substrate having a first surface and a second surface on both sides thereof, provided on the first surface being a light-incident plane via which a light beam is to be incident in recording or reproduction, formed alternately on the second surface being a plurality of first lands and first grooves, and a first organic-dye recording layer formed on the second surface to cover the first lands and grooves. The second structure has a second substrate, alternately formed on which are a plurality of second lands and second grooves, a reflective film formed on the second transparent substrate to cover the second lands and grooves, and a second organic-dye recording layer formed on the reflective film to face the second transparent substrate. The first and the second structures are bonded to each other via a bonding layer so that the first and second recording layers are provided between the first and second substrates. A formula .alpha.1.gtoreq.cos.sup.-1(20/Tb) is satisfied in which Tb is a thickness of the reflective film formed on a bottom of each second groove and .alpha.1 is an angle between a plane passing through an upper surface of each second land and a side wall of each second groove.